It is a grim sight for wildlife officials
working in the Rocky Mountains on the border of Colorado and Wyoming, one
of only two spots in the world where the disease has appeared. For health
officials, a frightening question must be answered: Will this terrible
illness cross over to the human population?

The National Institutes of Health is
investigating because mad cow disease, similar to the chronic wasting disease
that has struck mule deer and elk, has been linked to a brain-wasting malady
in humans -- Creutzfeldt-Jakob disease -- that has killed 20 people in
Europe.

"We know there's a link between
the diseases, not a causal link necessarily, but they're the same kind
of disease," said Byron Caughey, biochemist at the NIH's Rocky Mountain
Laboratories in Hamilton, Montana.

"Of great interest is whether we
have to worry about it being transmitted into other animal hosts, whether
cattle or humans," he said.

About 6 percent of mule deer in the area
of northern Colorado and southern Wyoming suffer from chronic wasting disease,
or CWD, said Todd Malmsbury, spokesman for the Colorado Division of Wildlife
in Denver.

There are an estimated 550,000 mule deer
-- a brown, white-tailed species with big ears -- in all of Colorado.

Like mad cow disease, or bovine spongiform
encephalopathy, and the new strain considered its human equivalent, Creutzfeldt-Jakob
disease, CWD destroys brain tissue and kills its victims.

Both Creutzfeldt-Jakob and CWD leave
spongelike holes in victims' brains.

Creutzfeldt-Jakob may lie dormant for
years, but once symptoms appear -- loss of muscle control and dementia
-- it quickly destroys the brain.

It is rare, afflicting just one in a
million people annually in the United States. But it's fatal, killing about
seven months after symptoms appear.

All three diseases -- mad cow, Creutzfeldt-Jakob
and the wasting disease -- are blamed on infectious rogue proteins called
prions, which are mutant versions of proteins that occur normally in the
body.

An American biochemist, Stanley Prusiner,
won the Nobel Prize in medicine in October for discovering the Jekyll-and-Hyde
protein that causes these brain-destroying illnesses. Prions are considered
an entirely new type of disease-causing agent, distinct from bacteria,
viruses, fungi or parasites.

No one has become sick from carrying
the wasting disease -- but wildlife officials require hunters to turn in
the heads of deer or elk they've killed. If the brains test positive, the
hunters are advised to dump the meat.

Forty deer turned in during the past
hunting season tested positive, Malmsbury said.

While the NIH is interested in whether
the wasting disease can jump to humans, federal and state agencies have
launched three studies to determine its transmissibility to cattle, said
Mike Miller, a state wildlife veterinarian.

In Iowa, researchers are injecting brain
material of infected wildlife into the brains of cattle. At the University
of Wyoming, infected brain material is being given to cattle orally.

In addition, researchers are investigating
whether the disease can be spread through contact, letting cattle live
with deer herds that have contained infected animals.